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#### Performing an Upper Level Matrix Calibration

After you've finished calibrating the lower level matrix, you can perform the regular calibration. This upper level calibration calibrates the actual probe tips. It also sends another matrix of numbers to the controller that gives small corrections to the lower level matrix based on the current probe configuration and orientation.

To achieve greater accuracy, PC-DMIS should take probe hits, measuring a full sweep, all around the equator of the calibration sphere. You will get better results if you have a good angle of coverage on the sphere. You can control the start and end angles for the sweep around the sphere's equator from these registry entries in the ProbeCal section in PC-DMIS Settings Editor:

FullSphereAngleCheck - Set its value to 25.0

ProbeQualToolDiameterCutoff - Set its value to 18.0

ProbeQualLargeToolStartAngle1 - Set its value to 50.0

ProbeQualLargeToolEndAngle1 - Set its value to 310.0

ProbeQualSmallToolStartAngle1 - Set its value to 70.0

ProbeQualSmallToolEndAngle1 - Set its value to 290.0

For information on modifying registry entries, see the "Modifying Registry Entries" chapter in the PC-DMIS Core documentation.

Calibration Procedure

Follow this procedure to do an upper level matrix calibration:

1. Open the Probe Utilities dialog box (Insert | Hardware Definition | Probe).

2. Click the Measure button.

3. In the Type of operation area, select Calibrate tips.

4. In the Calibration mode area, select User defined. Since the Default method only takes hits around the diameter and one hit on top of the calibration sphere, it doesn't give a very good 3D relationship of the probe center. However, if you want to calibrate using the Default method, be sure to read "Notes on SP600 Default (2D) Calibration Mode" below.

5. In the Number of levels box, type 3. You can type in additional levels as long as they don't exceed the number of hits you'll be taking. But, the minimum number of levels should be at least three.

6. In the Start Angle box, type 0.

7. In the End Angle box, type 90.

8. In the Number of hits box, type 25. You can have PC-DMIS take as few as 12 hits, but it's generally recommended to take 25 hits.

9. Click the Measure button when you're ready to begin.

10. If you have turned on the analog probing hits option inside of the PC-DMIS Settings Editor, then PC-DMIS automatically takes 5 hits around the calibration sphere to better define the center of the calibration tool.

11. PC-DMIS then calibrates the AB angle positions and automatically writes the upper level matrix numbers to the controller. These numbers are correct if you correctly followed the lower level matrix calibration procedure.

PC-DMIS then displays the Probe Utilities dialog box. The active tips are now calibrated, and you're ready to program your measurement routine using the newly-calibrated SP600 probe.

Notes on SP600 Default (2D) Calibration Mode

In the Calibration mode area, if you select Default, PC-DMIS inserts five hits into the Number of hits box. When you begin the calibration procedure, PC-DMIS takes these hits on the axes normal to the probe position.

Be careful if you attempt to calibrate under these three conditions:

- You have a shank on the calibration sphere that comes out of the bottom (vector is 0, 0, 1).

- You use the Default calibration mode.

- You have an A90 angle in spheres.

If the above conditions are met, PC-DMIS crashes the probe into the shank of a calibration sphere. This happens because the probe tries to take a hit in the Z- position of the sphere.

To fix this, use an inclined shank, don't calibrate tips that have A90 angles, or choose to use the User defined calibration mode.